The 184th mitzvah is that we are commanded to remove obstacles and dangerous objects from our dwellings, i.e., to build walls surrounding roofs, wells, trenches, etc. in order to prevent people from falling into them or from them. The same applies to all dangerous places — they should be built and repaired in a way that prevents any danger.
The source of this commandment is G‑d's statement,1 "[When you build a new house] you must place a guard-rail around your roof."
In the words of the Sifri "The phrase 'You must place a guard-rail' constitutes a positive commandment."
The details of this mitzvah are explained in tractate Bava Kama.2
